In recent years, an increasing desire for alternatives to replace traditional non-degradable petroleum-based plastics has motivated deriving polymeric materials from annually renewable natural resources. Of great interest and environmental importance are aliphatic polyesters, such as polylactide materials, which are attractive polymer materials, because of their stiffness and tensile strength. Aliphatic polyesters may be used for disposable or durable molded resin applications.
Conventional methods have blended the polylactides with petroleum non-renewable materials or rubbery materials to toughen polylactides; however, control of the morphology and dispersion has been difficult. To achieve a desirable two-phase morphology while retaining the biorenewability and degradability of the polylactide composite, the present inventors blended vegetable oil with the polylactide. Despite the benefits of the blend, polylactide and vegetable oil are highly immiscible with one another and are difficult to mix, in part due to a large viscosity difference between the two components. Accordingly, improved blends of polylactide and vegetable oil as well as improved methods of blending and controlling the blends are desirable.